Not sure if this has been posted elsewhere, but if you buy a 500ml bottle of Erdinger at Sainsburys, you get the £5 glass with the boss's smiling face on it for free.
I just nipped in and the shelf had the beer (£1.85) and the glasses (£5), but didn't show the offer.
I was going to grab 2 of each anyway - 1 for me, one for my Dad for Sunday and when I got to the till, it knocked off the £10.
So go grab 'em while they still have some.